Edward Lotter wrote:
> 
> Try as I might (and search as I might) I have not been able to find a
> solution to this one!
> 
> My first thought (when learning POV-Ray) was a light that looked like a
> cyclinder.
> The docs do NOT tell you that the light will ONLY emit from the source, not
> the
> entire object.
> 
> Okay, next try. Halos! Many frustrated hours later. NOPE!
> 
> Finally, linear area lights!! Even more frustrated hours later. I don't
> think so!!

[snip]

> How does one render a visible flourescent tube (like those in an office
> ceiling)?
> Or even a neon sign??

Um... don't forget that neon tubes work differently from fluorescent
tubes. In a neon tube, the gas glows in the colour that you want. you
can see through the glass tube (I'm pretty sure about this, but not
absolutely.) I don't think they use tinted glass either.

In a fluorescent tube, the inside of the glass tube is coated with stuff
(magic powder, I guess) that absorbs the non-visible ultra-violet light
and emits it as visible not-quite-white light.

I guess that what I'm driving at is that a fluorescent light tube could
simply be an opaque cylinder with a high ambient, whereas the neon tube
should probably have something like a cylindrically-mapped halo, and the
glass tube itself really should be the difference between two cylinders,
with some refraction applied.

Of course this would only make a difference in extreme closeup views,
and I haven't even attempted to deal with how to make it look like a
convincing light source. (Although, somebody's idea of using greater
than 1 values in the colour vectors, and switching on radiosity sounds
pretty good, especially for the neon signs.)

Or... take a different tack:
Render a view of the neon sign only, possibly with an orthographic
camera. Use a black background. Take that image and run it several times
through a blur filter in PhotoShop (or whatever). If you don't have a
suitable image editor, then render the neon sign with a lot of
focal_blur [not sure of what the keyword really is, but you get the
idea].
Finally, take that blurry image and map it onto the wall or board that
the sign is attached to. I bet it would look pretty close, but I haven't
actually tried anything like it.

-jr- 

**********************************************
* Delete "spamBgone." to get my real address *
**********************************************

Post a reply to this message